Surgical robots with complex maneuvering capabilities are able to perform surgery by entering the body through tiny incisions. This less invasive approach results in decreased blood loss, significantly reduced recovery time, and lower overall healthcare costs when compared with traditional open surgery. For these reasons, robotic surgical systems are becoming a valuable asset to most major surgical centers. However, the use of surgical robots is currently limited to a small number of simple procedures because of one constraint: the design of current surgical robotic tools fails to provide the surgeon with an adequate sense of the forces being exerted on the tissue by the surgical instruments. This sensory input, termed tactile perception, is vitally important to medical professionals during surgical manipulation of tissue.
In traditional surgery, surgeons use the tactile perception of their fingertips to ascertain how hard to pull and grasp tissue without causing unwanted damage. Surgeons also use their tactile perception to assess the stiffness, density or texture of different tissues to determine what type of tissue it is. In minimally invasive robotic surgery, this tactile perception is lost and surgeons are left “blind” as to touch. This lack of haptic sensation poses the risk of unnecessary tissue damage and loss of valuable tactile information, and in many surgeries this risk outweighs the benefits that accompany robotic surgery. Thus; robotic surgery is excluded from use in many surgical procedures where it would prove extremely useful.
Ideally, a surgical tool for use in minimally invasive surgery would satisfy several criteria. Such a tool may include sensors capable of providing accurate and physiologically relevant information to the surgeon at appropriate spatial resolution. Sensors should be able to provide accurate measurements within the large range of pressures experienced at the tip of the graspers which range from very low levels up to pressures of 900 kPa. Further, the tool would possess a tissue-tool interface that allows appropriate grasping and manipulation of tissues and a profile that does not damage surrounding, non-target tissue.
Many research groups have attempted the design of surgical instruments that provide improved force and tactile perception to the surgeon; however, these efforts have not generated an appropriate tool for surgical use. One group attached strain gauges on the grasper jaws that bend with the grasper jaws and output a voltage signal corresponding to the amount of force exerted. Dargahi J., Najarian S. “An endoscopic force position grasper and minimum sensors,” Canadian Journal of Electrical and Computer Engineering, (2004) 28: 151-166. The design disclosed therein is able to determine the magnitude and location of a force within the jaws but does not provide force distribution maps that may be beneficial to a user.
Rosen et al. disclosed design of a remote control handle coupled to a pair of graspers. Rosen, J., Hannaford, B., MacFarlane, M., and Sinanan, M., “Force controlled and teleoperated endoscopic grasper for minimally invasive surgery—Experimental performance evaluation.” IEEE Transactions on Biomedical Engineering, (1999) 46: 1212-1221. Using optical encoders and actuators, the apparatus relays forces exerted at the instrument's jaws to the teleoperated unit. This design can potentially provide valuable information about local tissue compliance but utilizes only one bulk measurement that lacks adequate spatial resolution, potentially causing the surgeon to generalize inappropriately to a large tissue region.
Other groups have used microelectromechanical systems (MEMS) technology to develop sensor arrays to provide pressure distribution maps. Dargahi J., Najarian S. “Theorhetical and experimental analysis of a piezoelectric tactile sensor for use in endoscopic surgery” Sensor Review, (2004) 24:74-83; Heo J., Chung J., Lee J., “Tactile sensor arrays using fiber Bragg grating sensors” Sensors and Actuators A: Physical, (2006) 126:312-327; Peng P., Sezen A., Rajamani R., Erdman A. “Novel MEMS stiffness sensor for force and elasticity measurements” Sensors and Actuators A, (2010) 158:10-17. However, these designs have limited utility due to a lack of functional integration into endoscopic tools (i.e., they are unable to adequately manipulate tissue), inadequate resolution due to the size of the force transducers, and/or possess low upper limits of pressure ranges that are inappropriate for surgical application.
King et al. reported on an innovative design to be used with the Da Vinci robot which provides a low-resolution force distribution via an array of piezoresistive force sensors. King C., Culjat M., Franco M., Bisley, J., Cannan G., Dutson E., Gnmdfest V., “A multielement tactile feedback system for robot-assisted minimally invasive surgery” IEEE Transactions on Haptics, (2009) 2:52-56. Information from these sensors is then transmitted to 2×3 tactile display placed on the Da Vinci control unit at the surgeon's fingertips. The limitations of this design are spatial resolution and certain inaccuracies associated with the use of piezoresistive force sensors. Their system also lacked a functional grasping surface.
Thus, there remains a longstanding, unresolved need in the medical community for surgical tools used in minimally invasive surgery that have an effective dynamic range of force measurement and sufficient spatial resolution to selectively and effectively manipulate the target tissue, while at the same time minimizing damage to surrounding non-target tissue. Further, the profile of such surgical tools should be such that it has minimal impact on the tissue through which it passes en route to the target tissue. The present disclosure addresses these needs.